Experimental study of aerosol release following liquid leaks of fission products concentrates simulants (original) (raw)
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Nuclear Engineering and Design, 2013
h i g h l i g h t s Experiment investigating aerosol retention within concrete containment cracks under nuclear severe accident conditions. Provided representative conditions of the aerosols suspended inside the containment of PWRs under a severe accident. Prototypical aerosol particles generated with a thermite reaction and transported through the crack sample reproducing surface characteristics, temperature, pressure drop and gas leakage. The results indicate the significant retention due to zigzag path.
2013
The Waste Treatment and Immobilization Plant (WTP) at Hanford is being designed and built to pretreat and vitrify waste currently stored in underground tanks at Hanford. One of the postulated events in the hazard analysis for the WTP is a breach in process piping that produces a pressurized spray with small droplets that can be transported into ventilation systems. Literature correlations are currently used for estimating the generation rate and size distribution of aerosol droplets in postulated releases. These correlations, however, are based on results obtained from small engineered nozzles using Newtonian liquids that do not contain slurry particles and thus do not represent the fluids and breaches in the WTP. A test program was developed to measure the generation rate, and the release fraction which is the ratio of generation rate to spray flow rate, of droplets suspended in a test chamber and droplet size distribution from prototypic sprays. A novel test method was developed t...
Large-Scale Spray Releases: Initial Aerosol Test Results
2012
One of the events postulated in the hazard analysis at the Waste Treatment and Immobilization Plant (WTP) and other U.S. Department of Energy (DOE) nuclear facilities is a breach in process piping that produces aerosols with droplet sizes in the respirable range. The current approach for predicting the size and concentration of aerosols produced in a spray leak involves extrapolating from correlations reported in the literature. These correlations are based on results obtained from small engineered spray nozzles using pure liquids with Newtonian fluid behavior. The narrow ranges of physical properties on which the correlations are based do not cover the wide range of slurries and viscous materials that will be processed in the WTP and across processing facilities in the DOE complex.
Nuclear Engineering and Technology, 2016
The containment response during the first 24 hours of a low-pressure severe accident scenario in a nuclear power plant with a two-loop Westinghouse-type pressurized water reactor was simulated with the CONTAIN 2.0 computer code. The accident considered in this study is a large-break loss-of-coolant accident, which is not successfully mitigated by the action of safety systems. The analysis includes pressure and temperature responses, as well as investigation into the influence of spray on the retention of fission products and the prevention of hydrogen combustion in the containment.
Journal of Nuclear Materials, 2016
During reactor operation the fission gases Kr and Xe are formed within the UO 2 matrix of nuclear fuel. Their quantification is important to evaluate their impact on critical parameters regarding the fuel behaviour during irradiation and (long-term) interim storage, such as internal pressure of the fuel rod and fuel swelling. Moreover the content of Kr and Xe in the plenum of a fuel rod and their content in the UO 2 fuel itself are widely used as indicators for the release properties of 129 I, 137 Cs, and other safety relevant radionuclides with respect to final disposal of spent nuclear fuel. The present study deals with the fission gas release from spent nuclear fuel exposed to simulated groundwater in comparison with the fission gas previously released to the fuel rod plenum during irradiation in reactor. In a unique approach we determined both the Kr and Xe inventories in the plenum by means of a puncturing test and in leaching experiments with a cladded fuel pellet and fuel fragments in bicarbonate water under 3.2 bar H 2 overpressure. The fractional inventory of the fission gases released during irradiation into the plenum was (8.3 ± 0.9) %. The fraction of inventory of fission gases released during the leaching experiments was (17 ± 2) % after 333 days of leaching of the cladded pellet and (25 ± 2) % after 447 days of leaching of the fuel fragments, respectively. The relatively high release of fission gases in the experiment with fuel fragments was caused by the increased accessibility of water to the Kr and Xe occluded in the fuel.
Annals of Nuclear Energy, 2020
Prediction of the rate of fission product vaporization from a liquid metal pool to an overlying cover gas is important to both operational and safety (source term) considerations of fast reactors. The fission product vaporization rate can be strongly influenced (enhanced) by the simultaneous presence of a metal fog in the cover gas boundary layer just above the surface of the metal pool. The metal fog droplets can scavenge fission product vapor and thermophoretically drift away from the metal pool, carrying their inventory of scavenged fission products. An algebraic model for predicting the rate of release of fission products from liquid metals to the overlying cover gas is presented here based on the notion that the fission product release rate is insensitive to the details of the metal fog droplet size distribution-a notion suggested by a simple one-dimensional stagnant film model of fission product scavenging by metal fog droplets in the cover gas boundary layer; and that leads to the conclusion that, for sufficiently lean metal fog droplet concentrations, the fission product vaporization rate is limited by the metal vaporization rate rather than the scavenging ''power" of the metal fog droplets. The metal vaporization rate which drives the fission product release rate is itself enhanced by the conversion of metal vapor to metal fog in the cover gas boundary layer. Available models for prediction of the enhanced metal evaporation in the presence of ''fogging" are reviewed here and modified to extend their range of applicability up to the boiling point of the metal. The facility with which the model of fission product release can be used for absolute predictions and comparison with available data is illustrated for the case of NaI release from liquid sodium into argon and nitrogen atmospheres. An available NaI released mass measurement and the model show that because of metal fogging fission product vaporization rates can exceed the rates predicted by conventional mass transfer theory by as much as an order of magnitude. Finally, the application of the fission product vaporization rate model, which incorporates both the liquid metal pool and cover gas resistances to mass transport, is used to calculate the ''escaping strengths" of a number of important fission products from liquid sodium, lead, and lead-bismuth eutectic pools.
Volume 7: Decontamination and Decommissioning, Radiation Protection, and Waste Management; Mitigation Strategies for Beyond Design Basis Events
The general context of the article is related to the development of the laser cutting technique for the fuel debris retrieval on the damaged reactors of Fukushima Dai-ichi. IRSN and CEA are involved in a project, led by ONET, to bring relevant elements to analyze the risk occurred by the dispersion of aerosols emitted by the dismantling operations. Results regarding the aerosols source term characterization emitted during laser cutting of non-radioactive fuel debris simulants were acquired during experiments undertaken on the DELIA cutting laser platform from CEA. IRSN realized aerosol sampling, aerosol size distribution measurement and CFD calculation of aerosol transport and wall deposition. The evaluations performed will enable the Japanese teams responsible for extracting corium from the damaged reactors of Fukushima Dai-ichi to define the best strategies to implement containment, and ultimately to limit the dissemination of radionuclides in the environment.
2020
KAERI has been developing a design and analysis technique for a pool-type sodium-cooled fast reactor called Prototype Gen-IV Sodium-cooled Fast Reactor (PGSFR) since 1987 [1]. To this end, KAERI and Fauske & Associates, LLC (FAI) jointly developed the ISFRA (Integrated SFR Analysis Program for PSA) computer program to simulate the response of the PGSFR with metal fuel during a severe accident [2]. The ISFRA computer program adopts the aerosol correlation technique of Epstein et al. [3,4,5,6] to predict behavior of non-volatile fission product (FP) aerosols, tracking the suspended and deposited aerosol masses. The ISFRA aerosol model, which is based on the aerosol correlation technique, provides fast and stable calculations and is based on rigorous analysis. The governing equations for simultaneously coagulating and settling aerosols are transformed into non-dimensional equations based on aerosol similitude, where the particle size distribution reaches a log-normal distribution indep...
Nuclear Engineering and Design, 1988
An approach already presented to predict and correlate the aerosol suspended mass concentration for source-reinforced or aging aerosols undergoing coagulation and sedimentation is used here to develop correlations between the rate of aerosol deposition and the instantaneous aerosol suspended mass concentration. The functional forms of the correlations for the various deposition processes of interest in light water reactor safety are determined by numerical solution of the integrodifferential equation of coagulation and deposition. The applicability of the correlations to radiological assessments is then illustrated using several numerical examples relevant to water reactor safety.